INTERNAL COHESION OP LIQUIDS. 17 



cohesion now found to exist occupies an important as well 

 interesting place in the properties of liquids. 



Appendix (26tli April). — Previous Notices of the 

 Cohesion of Liquids. 



Besides the hanging of mercury in small gauges^ another 

 phenomenon^ which has long been known^ shows a small 

 degree of cohesion in water ; that is, that water will rise 

 up small tubes by capillary attraction as well in the receiver 

 of an air-pump as in air at the ordinary pressure. This 

 fact was shown before the Royal Society by Robert Hooke. 



Prof. Maxwell, in his 'Ti'catise on the Theory of Heat/ 

 p. 259, after commenting on the fact that water has been 

 raised to a temperature of 356° F._, without boiling, re- 

 marks : — " Hence the cohesion of water must be able to 

 support 132 lbs. weight on the square inch/' from which 

 it would appear that he recognizes cohesion as a property 

 of water, and considers that the possibility of raising the 

 temperature above the boiling-point is evidence of such 

 cohesion ; but I am not aware that he has anywhere given 

 his reasons for such a conclusion. 



I am indebted to Dr. Bottomley for reference to a paper 

 in the Ann. de Chim. et de Phys. (3) xvi. 167, by M. F. 

 Donny, in which M. Donny gives an account of experi- 

 ments in which he found that columns of sulphuric acid 

 could be suspended in vacuo to a height of 1*3 m^tre 

 (about 50 inches), showing a tension of about 7 inches of 

 mercuiy, care having been taken first to remove all the air 

 from the acid. M. Donny further describes experiments 

 made with water in exhausted tubes, in which he showed 

 the effect of cohesion by shaking the tube. M. Donny 

 does not, however, appear to have thought of the plan 

 which I adopted of making mercury adhere to the tubes by 

 wetting them with sulphuric acid or water. Not being 



SER. III. VOL. VII. c 



